At present, a mobile phone battery is generally charged first by a constant current and then by a constant voltage. The main process is as follows: constant-current charging is performed on the mobile phone battery; when the voltage of the mobile phone battery reaches a charging cutoff voltage, an actual voltage of the battery is partially virtual-high because of internal resistance of the battery, and the charging current needs to be lowered continuously, that is, the mobile phone battery continues to be charged by using a constant voltage until the virtual-high part is completely cleaned up, so that the charging is finished.
During the implementation of the present disclosure, it is found that the prior art at least has the following problems: in emergency cases, when the mobile phone battery needs to be fast charged, because a load capacity of a present charger is limited, the charger may be damaged because of overloading if a large current is output. For example, a nominal 5 V 500 mA charger may be damaged because the charger is overloaded if a current of 1 A is output. In addition, when a lithium-ion battery is charged with a large current, the internal temperature may rise because of the large current, and therefore a risk of battery overcharging exists.